Part 7 - Lore
Bethesda has exhibited a complete disregard for lore and established canon with Oblivion. We aren't talking about minor inconsistencies but glaring contradictions in Oblivion to facts about the game world that were established in previous games, a term the lore community has coined "lore rape".
1.Trading in Dwemer (Dwarven Artifacts) without a charter is considered treason in the empire and punishable by death. Yet, once you get to a high enough level, every town's local smith will have a supply of Dwemer Armor and Weapons. There aren't even any Dwemer ruins in Cyrodiil to begin with so where in the world are the weapons and armor coming from? And why would people openly commit what is considered to be treason against the empire?
2.Daedric armor and weapons are supposed to be rare. Maybe not as rare as in Morrowind but once you get to a high enough level, everyone and their dog has a pair. And Daedric then starts to become more common in the game world than iron or steel.
3.In Morrowind, the Emperor was on his death bed, very ill. Tension and strife was erupting in the empire because the Emperor's sons were believed to be dopplegangers placed by Jagar Tharn. Yet, suddenly within the span of only a few years, there isn't even a mention of this in Oblivion. The Emperor is old but appears perfectly health for a man of his age.
4.In Morrowind and in Redgard's "The Pocket Guide to the Empire", Cyrodiil was described as a vast jungle and rainforest. Mysteriously, in Oblivion, Cyrodiil is suddenly just a giant forest with no jungle-like characteristics and certainly no characteristics that would be typical of a rainforest (with the notable exception of the areas around Leyawinn).
5.Dunmer males have gone from having a deep, raspy/throaty voice to having one that sounds like a child on happy pills.